The subject disclosure relates to quantum computing, and more specifically, to techniques facilitating circuit design and fabrication for quantum computers.
As computer technology advances and conventional computing devices decrease in physical scale, a growing interest has been placed on quantum computing as a technique by which computing technology can continue to advance past the physical limitations of traditional computers. A quantum computer can operate via superconducting quantum logic circuits, which can include arrays of transmon qubits, capacitively shunted flux qubits (CSFQ), and/or other types of superconducting qubits linked by quantum buses. Cross-resonance (CR) gate operations in the circuit enable the implementation of quantum logic gates between qubits in the circuit. However, CR gates are sensitive to the relative frequencies of their corresponding qubits, and the behavior of respective qubits can define windows of relative frequencies for functional gates as well as collision windows, i.e., ranges of relative frequencies which can cause gate errors. For instance, as disclosed by Rigetti et al., “PROCESSING SIGNALS IN A QUANTUM COMPUTING SYSTEM,” U.S. Patent Application Publication No. 2016/0267032 A1 (reference numerals omitted), “[an] example quantum computing system includes multiple operating domains. Each of the operating domains can include dedicated hardware at one or more stages of the quantum computing system.” With respect to this example, Rigetti et al. further discloses that “the quantum processor includes an array of qubit devices, and each operating domain includes a particular group of the qubit devices and the associated devices and other hardware that operate in connection with the particular group of qubit devices. The devices in each group have distinct operating frequencies . . . ” Rigetti et al. additionally discloses that “each qubit device and its corresponding readout device operate within a frequency band, and the frequency band for each qubit and readout device pair is separate and distinct (non-overlapping) with the frequency band for the other qubit and readout device pairs within the same operating domain.”
Due to uncontrollable variations and/or imperfections in nano-structures utilized during device fabrication, the frequency of single-junction qubits cannot be precisely set or controlled. As a result, in a given lattice of fixed-frequency qubits employing CR gates, a significant number of frequency collisions can exist that can adversely impact the performance of the respective qubits. In view of at least the above, there exists a need in the art for techniques to accommodate frequency imprecision associated with qubit circuit fabrication.